The present invention relates to a torque transducer and, more specifically, to applications of a torque transducer and associated controller coupled to a hydraulic power unit.
Measuring the torsional forces acting on a shaft, particularly a power shaft, is often desirable. Hydraulic power units such as pumps, motors, transmissions, valves, and steering units are used to convert and transmit power between devices in many types of equipment. For example, a hydraulic pump may convert the power of an internal combustion engine or other source into a flow of high pressure hydraulic oil that can be used for performing a useful function in a machine. This flow of high pressure oil may be used to power a hydraulic motor that propels a wheel or track in a vehicle such as a tractor, bulldozer, or crane. In other instances, this flow of high pressure oil may be used to operate hydraulic cylinders that perform such functions as manipulating the excavation bucket on a back hoe or for another device.
The primary measurements that are useful for determining performance and controlling hydraulic power units are the fluid pressure, fluid flow, shaft rotation speed, and shaft torque. Pressure, flow, and speed are routinely measured with readily available sensors. In the past, pressure and flow sensors have been integrated into hydraulic power units such as hydrostatic pumps and motors. Examples of using speed sensors are given in U.S. Pat. No. 5,325,055.
Several technologies are available for measuring the torque experienced by a rotating shaft. Many of these common technologies, often called “contact” torque transducers, utilize strain gauges, sensors, or radio transmitters that are attached to the rotating shaft. Further, many of these technologies have integrated contact type torque transducers into a hydraulic power unit.
Non-contact torque transducers also have been developed in the prior art. An example of such a device is shown in U.S. Pat. No. 5,052,232. In this system, the rotating shaft is circularly magnetized in such a manner that a measurable axial magnetic field is created outside of the shaft which is indicative of the torque experienced by the shaft. The prior art has also demonstrated the integration of a magnetoelastic torque transducer into a hydraulic power unit. An example of the integration of a magnetoelastic torque transducer into a hydraulic power unit is shown in U.S. Pat. No. 2003/0172747 to Gandrud.
While these torque transducers have been integrated into hydraulic power units, the prior art has not developed applications for use with torque transducers in association with hydraulic power units. Further, the prior art has not integrated a controller with a hydraulic power unit equipped with a torque transducer.
It is therefore a principal object of this invention to provide a system and method for monitoring the torque imposed on a shaft of a hydraulic power unit.
A further object of this invention is to provide a hydraulic power unit with a torque transducer and a controller associated with the transducer to monitor the measured torque.
Yet a further object of the present invention is the application of an integrated torque sensing technology that can be produced at a cost which will enable its use on a volume production basis.
Still a further object of the present invention is the application of a torque sensing technology that is sufficiently compact to provide for installation within hydraulic power units.
These and other objects will be apparent to those skilled in the art.